If we're laying it all out, even Monsters isn't guaranteed use for Universal Parks. There is footage of a main house designer given a description of Legends Collide and saying something to the effect of "We have been very gracious that we've been allowed to tell some original stories with these characters". Because as much as a lot of people love to lump Frank and Wolfman in the Original House category, they are 100% IP. There are negotiations that have to be made to make even a house like Brides happen at all.
Yep. This was especially true when they were preparing to launch the Dark Universe - HHN Hollywood's relaunch was intended to coincide with that (and was originally to be titled "Dark Universe"). Even though that project fell apart, the Universal Monsters have become a relevant brand again in the eyes of the company. It's why you see so many new partnerships, merchandise lines, and high-end releases. They care about how the Monsters are presented in the Universal parks (and whether it may conflict with how they intend to approach/position a character for a forthcoming movie).
Agreed, as much as I like to think to consider the UCM houses as originals due to taking them in original directions, they're still very much a IP/Licensed property that A&D needs to get permission to use. This is further backed up by the UTM tours, since IP's usually have the most restrictions on where you can take photos. Sure enough, in the three-house tour last year (Bride of Frankenstein LIVES, Revenge of the Tooth Fairy, Case Files.), Bride of Frankenstein LIVES was the most restrictive since there were only three rooms we could take pictures in. Compare that to Case Files, a fully original property, where there were only three rooms we couldn't take pictures in.